1. Technical Field
The present invention relates to an electrophoretic display device.
2. Related Art
An active matrix type electrophoretic display device includes switching transistors and memory circuits in pixels (for example, see JP-A-2005-114822). In the display device described in JP-A-2005-114822, an electrophoretic element including a plurality microcapsules, in which charged particles are included, are adhered on a device substrate on which pixel switching transistors or pixel electrodes are formed and the electrophoretic element is sandwiched between the device substrate and a counter substrate on which counter electrodes are mounted.
Each of the pixel circuits of the electrophoretic display device is preferably laid out such that a circuit area is reduced in order to realize high-precision display. Accordingly, it is preferable that the number of lines in each of the pixel circuits is small. For example, in each of the pixel circuits of a liquid crystal device which is an example of the display device, one capacitor and one transistor are mainly used. In this circuit, a selection transistor connected to a scan line and a data line and a capacitor connected to a ground line or a scan line of an adjacent pixel are configured. A line which is necessary in each of the pixel circuits is only a line for connecting the transistor and the capacitor and a line with the ground line or wiring area between the pixel circuits offers no problem.
In contrast, each of the pixel circuits of the electrophoretic display device includes a latch circuit as a memory circuit and two transmission gates controlled to deliver an external signal to a pixel electrode by data stored in the latch circuit. By this circuit configuration, a display state can be changed to an entirely white image, an entirely black image and a reversed image while maintaining image data in the latch circuit. A driver circuit does not need to be operated except when a new image is displayed and a flexible display method can be realized.
However, in each of the pixel circuits having the latch circuit and the transmission gates, a pixel selection switch circuit, the latch circuit and the transmission gates need to be included in a layout region of one pixel; and connection of lines for connecting these components, positive and negative power source lines connected to the latch circuits, and global lines called external signal lines are required. If the lines from the global lines are arranged to be longitudinally crossed, the connection between the components needs to avoid the lines, the lines become complicated, and a necessary space is increased. In particular, since a wiring area is increased, an area per pixel is increased and high precision cannot be realized.
If the components such as the pixel selection switch circuit, the latch circuit and the transmission gates are arranged in a restricted area, that is, one pixel, the gap between the lines may be small. In this case, since particles may be attached between the lines and a short circuit may occur in a manufacturing process, yield may deteriorate.